On the Magnetic Susceptibility of Aromatic Hydrocarbons and ``Ring Currents''

Abstract

It is shown that the anisotropic magnetic susceptibility (and chemical shift) of aromatic hydrocarbons generally attributed to π-electron ``ring currents'' can be correctly represented as the sum of contributions from localized electrons of both π and σ character. The ``delocalization'' of the electronic distribution plays no part whatever is the effect and is only an artifact of London's approximate calculation. Anisotropic Pascal's constants for aromatic carbon atoms are determined empirically and excellent agreement with the experimental anisotropic susceptibilities is obtained.